Display devices have typically used cathode-ray tubes (CRT). Various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDP), field emission displays, and electro-luminescence displays (ELD), have been studied as a replacement for the CRT display. LCD devices have advantages over flat panel displays, including high resolution, light weight, thin profile, compact size, and low power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other. A voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device includes a backlight to facilitate displaying of images. According to the arrangement of the backlight, the LCD device is categorized as an edge-type or a direct-type. The backlight of the edge-type LCD device is arranged at a side of the LCD device, and the backlight of the direct-type LCD device is arranged below a liquid crystal panel. Further, the backlight may be categorized as a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL) and a non-electrode type lamp. The CCFL has internal electrodes, and the EEFL has external electrodes.
FIG. 1 is a cross-sectional view illustrating a direct-type LCD module having EEFLs according to the related art. The LCD module includes a liquid crystal panel 10, a backlight assembly 20, a main support 30, a top case 40 and a bottom case 50. The liquid crystal panel 10 includes first and second substrates 12 and 14 and a liquid crystal layer between the two substrates 12 and 14. The backlight assembly 20 includes a reflecting sheet 22 on the bottom case 50, a plurality of EEFLs 24 on the reflecting sheet 22 and a plurality of optical sheets 26. The main support 30 supports the backlight assembly 20 and the liquid crystal panel 10 sequentially placed therein. The top case 40 presses against and fixes a peripheral portion of the liquid crystal panel 10 and is coupled with the bottom case 50. Each EEFL 24 includes a lamp tube and two external electrodes, each at opposite end portions of the lamp tube. The two external electrodes are supplied with lamp driving voltages from corresponding common electrodes.
FIG. 2 is perspective view illustrating a coupling structure of EEFLs and a common electrode in an LCD module according to the related art. The coupling structure at one of the end portions of the EEFLs is shown in FIG. 2, which is the same as the coupling structure at the other end. Each EEFL 24 has two external electrodes 28 on outer surfaces of each of the end portions of a lamp tube. A pair of common electrodes 23 are located at each end portion of the EEFLs 24 and are connected to the corresponding external electrodes 28. The common electrode 23 includes a base portion, a plurality of lamp holders 27 and a plurality of stoppers 25. The base portion includes first and second lines 29a and 29b. Three lamp holders 27a, 27b and 27c corresponding to the external electrode of each EEFL 24 fixes the EEFL and supplies a common voltage to the EEFL. The stopper 25 prevents the EEFL 24 from moving in an axial direction of the EEFL 24.
As described above, at least three lamp holders are used to firmly fix the external electrode of the EEFL. Accordingly, a contact area of the lamp holders and the external electrode is large. This causes current flowing on the common electrode to increase. Accordingly, power consumption increases and current leakage may occur.